Safety mechanism for material handling machines



May lo 1932- c. H. WAGNER 1,857,172

SAFETY MECHANISM FOR MATERIAL HANDLING MACHINES Filed D60. '7, 1928 Tsl. I 0

hrw/ Wag/zar Patented May. 10, 1932 PATENT OFFICE CHARLES H. WAGNER, F WASHINGTON, DISTRICT OF COLUMBIA, ASSIGNOR T0 KOEHBING COMPANY, 0F MILWAUKEE, WISCONSIN, A CORPORATION SAFETY MECHANISM FOR MATERIAL HANDLING MACHINES Application led December This invention relates to port-able material handling excavating machines and more particularly to cranes and the like provided with adjustable booms carried by portable supports.

At the present time when machines of the above type are operated, the operator cannot with accuracy determine the exact Vweight of the load being handled. It is also impossible for the operator to determine with accuracy the distance of the load from the support or traction base of the crane. Consequently with both of the factors unknown or uncertain it is not infrequent that the operator attempts to lift a load greater than the counterbalancing eiect of the machinery and counterweights within the car body. Even though the operator is highly skilled, the machine may be overturned, causing vgreat damage to property and occasionally loss of life.

Cranes operated in conjunction with clam shell buckets when excavating sticky mud or clay are frequently overturned due to the inability of the operator to determine the exact J load imposed upon the end of the boom. Consequently it is necessary for the operator to be very cautious yand careful, otherwise serious damage may result by this overturning due to the suction caused by the sticky nature of the material being excavated. Operators under these conditions oft-en operate their machines verg1 ineiiiciently.

I am aware that the manufacturers of excavating machines vhave attempted to prevent these accidents by providing charts and load diagrams indicating the safe loads for their machines when equipped with certain length booms and loads being handled at diiferent distances from the traction base of the machine. Charts are also provided to indicate the weights per cubic foot of different kinds of materials to be handled or excavated.

All of these factors are uncertain and, therefore, careful calculations must be made 43 in order to determine the safe load that can he handled. Even though the weight of the load is known when the boom support of the machine is rotated to deposit the load, centrifugal force acting upon the load due to this :m swinging action causes an outward move- '7, 1928. Serial No. 324,388.

ment of the load away from the support which creates a much greater leverage on the hoorn. Under these conditions if a maximum capacity load is being handled, the car body or boom support as itis rotated to swing` the load to depositing position will cause the load to move away rom the support. The increased leverage on the mac line caused thereby will actually produce an overturning thereof. Y

Itis also to be remembered that frequently the tag line of a clam shell bucket is operated to cause the loaded bucket to swing out beyond the end of the boom, which action creates a greater overturning stress on the crane.

An object of my invention is to provide a. safety mechanism for machines of the above type, which is entirely automatic in operation, to positively prevent the overturning of a material handling machine under any and all conditions ordinarily resulting from the handling of an overload. Y

Another object of my invention is to provide a safety mechanism for cranes and excavating machines and the like provided with hoisting booms, which is actuated by the load being handled to automatically indicate to the operator at all times the safe load which may be handled, irrespective of the distance of the load from the machine, and to subsequently indicate when an overload is being handled.

A further object is to provide a safety mechanism for portable excavators, cranes and the like, to automatically indicate to the operator thereof the maximum load capable of being lifted by the machine without overturning and to signal the operator when the maximum load has been reached.

A still further object is to provide an attachment for application to cranes and the like, operable incident to working conditions of the machine to indicate when a maximum predetermined lifting capacity of the machine is reached, and under these conditions cooperate with the lifting mechanism of the crane to render such mechanism inoperative to lift the load To the end of providing a safety device in accordance with the thoughts previously outlined and having in mind particularly the provision of instrumentalities for automatically indicating to the operator` of a crane the maximum safe load which may be liandled with the load supporting means at any particular angle with the boom. More particularly, I propose to avail of instrumentali ties which are actuated by a change in the angular relationship between the boom and cable which-supports the bucket, to vary the maximum safe load of the crane.

Other and further objects and advantages of the invention will be hereinafter set forth and the novel features thereof defined by the ap ended claims.

n the drawings:

Figure 1 is a side elevation of a portable crane having my invention ap )lied thereto, the full lines indicating a Weight heilig handled by the crane and the dotted lines indicating a clam shell excavating bucket;

Figure 2 is an enlarged sectional view approximately taken on line 2 2 of Fig. 1, showing my safety mechanism in detail, the crane connections and certain parts being omitted therefrom for the sake of clearness, circuits being shown diagrammatically. and dotted lines indicating the position of the parts when a greater load than the safe load capacity of the machine is imposed on the boom;

Fig. 3 is a detail view of the indicia carrymg segment;

Fig. 4 is a detail view of the indicator arm contact carrying member;

Fig. 5 is a detail view of the load operated contact closing lever; and

Fig. 6 is a section on line 6-6 of Fig. 2 showing the detail valve mechanism and bypass passages in the piston ofthe dash-pot.

Fig. 7 is a diagrammatic showing of the actuating lever for the bell crank which is pivoted to the end or peak of the boom.

Like numerals refer to like parts in the several iigures of the drawings in which:

A represents an excavating crane provided with a car body B rotatably supported on a traction base C and carrying the boom D from which is suspended the load E.

The engine F within the car body provides a source of power for operating the traction base C, rotating the car body B, and. actuating the cables G arrd G to change the angle of the boom D and to hoist or lower the load E. The cable G consists of a plurality of reeves or leads passing around pulleys D' supported on the outer extremity of the boom D and pulleys D" located on the A frame yoke 1. The yoke 1 is pivotally supported by the A frame 2. My safety device generally designated at H comprises in detail, as shown in Fig. 2, a segment 3 adjustably secured to a pin or trunnion 4 supported by the A frame yoke 1. This segment carries the safe load indicating indicia thereon, as indicated at 3'.

Mounted upon the pin 4, next to the segment 3, is a movable indicating lever 5, provided with the pointer 5 for cooperati with the indicia 3 to indicate the safe loa capable of being lifted by the machine for a given angle of the boom. This lever also carries the arm 5a supporting a yieldable contact 6. Actuation of the lever 5 incident to different angular positions of the boom to indicate the safe load which may be lifted, is effected by the connection 7 between the weighted hcll crank pivotally mounted on the inner portion of the boom D, and the lever. The connection 7 as shown, consists of allexible cable.

Lifting or peaking of the boom by the cables G elevates the bell crank 8 causing a slacking of the cable 7, whereupon the spring 9 will actuate the lever 5 to move the same to indicate a greater safe load capacity for the machine. Should, however, the boom be lowered, the cable 7, due to its connectionwith the boom carried bell crank 8, will actuate the lever 5 to indicate a smaller safe load capacity for the crane,

The bell crank 8 due to its uliar construction and mounting will a so cause the cable 7 to be pulled to actuate the lever 5, when thc car body is rotated with suliicient speed to permit centrifugal force to swing the load E out beyond the end of the boom, to indicate the safe load permissible under these conditions.

Th(l pin 4 also carries the pivoted contact lever 9 to which the dead end 10 of the boom hoist cable G is attached. A spring 11 provides a resilient connection between the outer extremity of the lever 9 and the A frame yoke 1, this spring being of suicient tension to cause the proper operation of said lever.

The lever 9 is provided on its opposite end with the contact 12 adapted to cooperate with the yieldable contact 6 on the lever 5 when this lever is actuated due to a load greater than the predetermined capacity safe load for the crane is handled.

In order t0 prevent the lever 9 from being actuated to close the contacts 6 and 12 before the inertia of the load being lifted is overcome, I provide the piston dash-pot 13 attached to the lever 9 at 14 and ivot/cd to the A frame voke at 15. This das -pot may of any approved construction, ut as dlsclosed in the drawings, it comprises the cylinder 13a filled with a suitable fluid in which a by-passed piston travels, having auxiliary valved openin s 13b to permit a relatively rapid return o the lever 9 when the pull on the dead end of the cable is relieved. To notify the` operator as the load being lifted exceeds the safe load of the machine for a. particular boom setting, I provide the audible signal 16, which closes the circuit 16' as the two Contacts 6 and 12 are brought together, thus permitting the battery 16a to actuate the signal.

lfVhen it is desired to positively prevent the machine from lifting a load greater than its capacity, I provide a supplemental circuit 17, as shown in Fig. 2 in dotted lines. lhen the contacts 6 and 1Q close this circuit, a short circuiting of the ignition device 18 of the engine F is effective, thus stopping the motor F and preventing the excessive load from being handled. The ignition device, as indicated at 18, is the commutator and distributor of the engine F.

In the operation of the crane excavator, as the operator winds up or reels out the cable G by the manipulation of certain control levers (not shown) the angularity of the boom D is changed which causes the clam shell bucket or load E being lifted to move closer to or farther aivav from the traction support C. Since the distance between the traction support and the load is directly proportional to the safe load capable of being lifted without overturning` it is easily understood that as the boom is raised and the load moved closer to the traction support, the lifting capacity of the machine is proportionately increased, whereas when the boom is lowered as the load moves awa from the traction support, the capacity of t 1e machine is proportionately decreased. The raising and lowering of the boom actuates the lever 5 to move the contact 6 farther awa or closer to the contact 12 on the lever 9. i ince the pull on the dead end 10 of the cable G is substantially proportional to the load on the boom I), it will be observed that for a. given load the position of the two contacts with relation to each other will bear a fixed relation to the angular position of the boom.

When the car body and boom are rotated, the pendulum effect of the Weighted bell crank 8 will cause a supplemental movement of the lever 5. 'Assuming that the operator desires to lift a load in excess of the safe caacity of the excavator for that particular oom angle, as the cables G are tensioned to lift the load, the arm 9 will be moved from the full line position, as shown in Fig. 2, to the dotted line position. As the dotted line position is reached, the contacts 6 and 12 close the circuit 16' causing the audible signal to sound, also closing the circuit 17 and short circuiting the motor, and positively reventing the load from being handled. switch 18 may be provided if desired to cut out this last circuit at the option of the operator of the machine.

As previously indicated, certain operations of the crane other than swinging and centrifugal force cause the loaded bucket to swing out beyond the end of the boom, particularly, stressing of the tag line together with gravity action creates this condition.

Bearing the possibility of this condition in mind, I provide the lever 19 which is pivotally connected to the upper end of the boom D. This lever 19 is provided with a roller 20 which engages the cable 21, supporting bucket E. A cable 22 connects the lever 19 with the bell crank 8 so that relative movement of the former with respect to the boom will aetuate the bell crank 8 to operate the indicating mechanism.

It is notable that the connection between the lever 19 and the bell crank 8 is positive for only one direction. This permits of outward swinging of the weight on the latter under centrifugal force immediately the crane is swung, thereby providing for a more prompt operation of the indicating mechanism than would be the case were the lever 19 to constitute its actuating means. It is noted however, that any outward movement ofthe lever 19 positively causes a corresponding movement of the bell crank 8. Furthermore, the effect of gravity on the latter maintains engagement between the roller 20 and cable 21.

Having thus described my invention. what I ciaim as new and desire to secure by Letters Patent is:

1. In a material handling machine, a traction support, a boom rotatably and angularly adjustable thereto and supported thereby, and an indicating device for preventing overtaxing of the machine including a load indicia carrying member. an indicator adapted to cooperate with said member and shiftable incident to adjustments of the boom, a circuit closing member shiftable incident to a load being handled by the machine to close a signaling circuit when said load exceeds the load indicated by the indicating member. resilient means for resisting movements of the circuit closing means, and supplemental means for preventing rapid movement of the contact llletlilS.

2. In a material handling machine, a traction base, a boom carrying support rotatably mounted thereon, a boom carried by the support and angularliy adjustable thereto, a load indicator carried by the support and shiftable incident to raising and lowering movements of the boom to indicate a predetermined safe load for a particular adjustment ot the boom. a supplemental load indicator associated with the previous mentioned load indicator, and means for adjusting the boom operable incident to a predetermined downward pressure on the end ofthe boom to automatically indicate when said pressure equals the predetermined safe load indicated by the first mentioned indicator.

3. The combination with a boom equipped material handling machine, of a gravity op-` erated indicator disposed thereon and arranged to shift incident to a change in inclination of the machine, means to shift the indicator upon a. change in the Working radius of the boom to indicate a. redetermined lifting capacityof the machine, a supplemental load operated member movably arranged to coo erate with the indicator incident to a pre etermined load bein handled by the machine, and means opera le due to said cooperation to indicate that the maximum load is being handled.

4. In a material handling machine, a support, a turntable carried thereby, a boom disposed thereon and arranged for angular ad- ]ustment, a load handling cable on the boom, an indicator member, means for shifting the indicator member for indicating a maximum predetermined load to be handled by the machine, means for shifting the indicator incident to variations in the angular adjustments of the boom and to shift the indicator incident to rotary swing of the boom, a supplemental load operated member movable by the load being handled by the machine and arranged to cooperate with the first mentioned indicator when the load handled equals the predetermined load as indicated by the first mentioned indicator, and means for indicating that said predetermined load is being handled when the first mentioned indicator cooperates with the said member.

In testimonyewhereof I aiix my signature.

CHARLES H. WAGNER.

CERTIFICATE 0F CORRECTIUN.

Patent No. 1,857,172.

my 1o, 1932,

CHARLES H. WAGNER.

lt is hereby certified that error appears in the printed specification of the above numbered patent requiring correction es follows: Page 3, line 97, claim l, strike out the article and word "a loa and insert the word an, and line 98, for "an" rend a load; and that the said Letters Patent should be read with these corrections therein that' the same may conformv to the record of the case in the Patent Office.

Signed and sealed this 12th day of July, A. D. 1932.,

(Seal) M.J.Moore,

Acting Commissioner of Patents.

dius of the boom to indicate a. redetermined lifting capacityof the machine, a supplemental load operated member movably arranged to coo erate with the indicator incident to a pre etermined load bein handled by the machine, and means opera le due to said cooperation to indicate that the maximum load is being handled.

4. In a material handling machine, a support, a turntable carried thereby, a boom disposed thereon and arranged for angular ad- ]ustment, a load handling cable on the boom, an indicator member, means for shifting the indicator member for indicating a maximum predetermined load to be handled by the machine, means for shifting the indicator incident to variations in the angular adjustments of the boom and to shift the indicator incident to rotary swing of the boom, a supplemental load operated member movable by the load being handled by the machine and arranged to cooperate with the first mentioned indicator when the load handled equals the predetermined load as indicated by the first mentioned indicator, and means for indicating that said predetermined load is being handled when the first mentioned indicator cooperates with the said member.

In testimonyewhereof I aiix my signature.

CHARLES H. WAGNER.

CERTIFICATE 0F CORRECTIUN.

Patent No. 1,857,172.

my 1o, 1932,

CHARLES H. WAGNER.

lt is hereby certified that error appears in the printed specification of the above numbered patent requiring correction es follows: Page 3, line 97, claim l, strike out the article and word "a loa and insert the word an, and line 98, for "an" rend a load; and that the said Letters Patent should be read with these corrections therein that' the same may conformv to the record of the case in the Patent Office.

Signed and sealed this 12th day of July, A. D. 1932.,

(Seal) M.J.Moore,

Acting Commissioner of Patents. 

